Detectability of close reflection peaks in ultrasonic NDT system has been significantly enhanced by using a diverse field algorithm. The CLEAN algorithm, which is popular in image processing of radio astronomy data, has been proposed in the case of ultrasonic testing. The feasibility study of the algorithm has been performed successfully in the application of ultrasonic signal processing and it is conceived that the algorithm might have good potential in ultrasonic NDT for distinguishing between close peaks and removing sidelobes.

Silver-copper alloys are condensed in a liquid-solid domain of the phase diagram on a tilted molybdenum substrate regulated in temperature. After a droplets regime, a film which contains a monolayer of nodular solid crystals forms. The size distribution and density of the particles in the film are measured after different condensation times. Results show that in our experimental conditions a ripening process occurs which is evidenced by a decrease of the number of particles with time, and a broad particle size distribution. However, the decrease rate is smaller than expected without a condensation flux. A model is then developed to interpret and generalize these results. This model results from the modification of the Lifshitz-Slyosov model [1] to take into account the supply from the vapour phase. It is shown that the higher the flux of material to solidify from the vapour phase is, the more the growth from the vapour phase overcomes the ripening process. Once the particle density reaches a characteristic value which is simply proportional to the incoming flux, no more particles are dissolved. The system then tends towards a monomodal distribution with a radius which grows in t1/3.

Two shape memory Cu-Al-Ni alloys, a polycrystal and a single crystal, exhibiting a martensitic transformation close to 130 °C (in the as-quenched state) have been studied. Specimens have been quenched after heat treatment at 850 °C. The structural evolutions of the high temperature phase (austenite) have been studied for thermal treatments performed below 200 °C. Investigations have been carried out using electrical resistivity measurements, TEM (Transmission Electron Microscopy) observations and X-ray diffraction analysis. The main structural modifications are observed in the polycrystalline alloy and concern first, the reordering process of the austenite structure (B2$\to$L21), and second, the precipitation of the (Cu9Al4) γ2 phase. In the single crystal alloy, the evolutions are very slight and localized on the structural defects. Particular attention is paid to the role of the quenched-in vacancy elimination on the observed mechanisms. In addition, the incidence of the structural evolution on the transformation temperatures is also discussed.

Sublimation and deposition of the metal-organic complex palladium (II) acetylacetonate [ Pd(acac)2] was investigated through thermogravimetry and XRD. The temperature range for sublimation, avoiding thermal decomposition, was determined to be 100−160 °C and required to take place in the presence of an inert gas such as helium. The complex was found to be highly unstable in the presence of hydrogen. The Clausius-Clapeyron equation determined is $\ln P = - 96 \times 10^3/RT + 29.26$. Deposition of the complex on monolithic substrates required the presence of adsorption sites. For the system investigated, change of the apparent deposition activation energy was found to take place within the range 100−150 °C. To obtain Pd metal particles, the precursor was reduced in hydrogen at a subsequent stage and temperatures close to room temperature were found to be sufficient.

This paper deals with the study of a new generation of ceramic matrix composites, SiCf-SiBC, which consists of a 2.5D perform of SiC fibers and of a self sealing multilayered matrix. Three different batches of these CMCs have been investigated in a morphological point of view thanks to the observations performed at the mesoscopic scale by scanning electron microscopy and automatic image analysis, and also at a microscopic scale by transmission electron microscopy. Through this study, a lot of care was taken about the description of the pyrocarbon interphase and of the different matrix interfaces, which play a key role in the damage features, and more specially in the deflection of the matrix microcracks developed through tested mechanical composites.

The electron temperature Te as the often most essential parameter for applications of low pressures plasma has been derived from comparative in situ measurements with a single and a double electrostatic probe, and with optical emission spectroscopy OES and energy dispersive mass spectrometry EDMS as remote techniques. Electrodeless rf discharges maintained by electron cyclotron wave resonance ECWR in pure Ar and N2 in the pressure regime from 10−2 to 1 Pa have been used as sample plasmas. The evaluation of the OES- and EDMS-signals is described in detail. The pressure dependence of the Te-results derived therefrom is found to compare well with the data from the probe measurements, and with calculations from a charge carrier balance equation. By matching the OES data to the absolute Te-values from the probe measurements, numerical expressions have been obtained by which Te can be quantitatively calculated from the intensity ratios between selected emission lines from the Ar- and the N2-plasma. Furthermore, the EDMS-results are also shown to deliver quantitative information about Te.

In this paper, electrical and acoustical characteristics of negative point-to-plane corona discharge loudspeakers are investigated. In the first part, the electrical behaviour of point-to-plane corona discharges is modelled by a three-parameters $(r_i, r_u, C_u)$ equivalent circuit. An experimental set-up for estimating these electrical parameters has been developed and improved. Based on the experimental results, evolution of the parameters with discharge conditions has been traced. In the second part, the electrode gap in negative point-to-plane corona discharges is divided into an ionisation region near the point, and a drift region. In each region, interactions between charged and neutral particles in the ionised gas lead to a perturbation of surrounding air, and so generate an acoustic field. For each region, seen as a separate acoustic source, an acoustical model is developed. An experimental set-up for measuring acoustic pressure has been developed, and allows us to confirm expectations based on directivity pattern, monopolar and dipolar directivities being associated to the ionisation and drift region respectively.

A conical resonator using the acoustic near-field technique has been designed and developed. This resonator design is sensitive to the density and viscosity of liquids, as well as to the modification, without discontinuity, of the rheological properties of viscoelastic media. The experimental measurements agree with the results expected from the modelling of the resonator.